Objective: Although sleep problems are common in the elderly and can affect cognitive functioning, there is debate about the best approach for assessing sleep difficulties as part of a neuropsychological evaluation. This study evaluated relationships between cognitive performances and sleep quality (measured both objectively and subjectively) in an older adult sample (age 59-94). Method: Participants were 31 individuals with mild cognitive impairment (MCI) and 93 age- and education-matched cognitively healthy controls (OA). Participants completed a comprehensive neuropsychological assessment, and kept a sleep diary and wore an actigraph for at least seven nights. Objective and subjective sleep data were used in regression models to predict standardized test performances of executive functioning. Results: Compared to controls, the MCI group showed poorer actigraphic sleep efficiency (SE) and greater wake after sleep onset (WASO), as well as poorer subjective sleep quality. After controlling for age, subjective report of sleep quality predicted performance on executive functioning measures in the OA group. In a separate regression model, actigraphically-measured sleep onset latency accounted for significant variance in executive functioning performance. For the MCI group, subjective sleep quality predicted executive functioning performance, whereas objective sleep measures did not account for variance in cognitive test findings. Conclusion: Although actigraphy can detect subtle differences in sleep quality between MCI and control groups, only subjective sleep measures were predictive of cognitive tasks in the MCI group. For cognitively impaired older adults, assessing perceived difficulties with sleep may be helpful in informing conceptualization of cognitive performance.